Giving small fry a helping hand

28 January 2010

Scientists have discovered that some female fish make up for mating with puny males by giving their eggs an extra injection of proteins essential for growth and development. The research, published this week in Proceedings of the Royal Society B, studied broad-nosed pipefish, which are unusual in the animal kingdom because females deposit eggs in males, who then care for the eggs until they hatch.

Both females and males prefer to mate with larger fish because they tend to produce larger and stronger offspring. The research team - led by Ines Braga Goncalves at the University of Gothenburg in Sweden - were interested in discovering whether females aim all their resources at favourable pairings with larger males, or whether they put up with smaller mates and compensate in some way.

They discovered that because there are limited numbers of large males, females are often left with no other choice than to leave their eggs with a smaller male. However, when required to mate with small fry, the females give their eggs an extra injection of protein, an important factor determining the embryo’s growth and development.

This is the first time that this kind of strategy has been observed in fish, and the researchers are now keen to find out more about the fishes’ reproductive habits by determining exactly why smaller males are perceived to be less good fathers. The results have wider significance for theories of mate choice, and lend credence to existing theories which say that compensation strategies only work under certain circumstances, including when males are in short supply.